(West Lafayette, IN) - It’s not too late for farmers to protect their crops or limit the damage from what’s described as an unprecedented invasion by the fall armyworm.
Reports of fall armyworms in significant numbers have come from states as far north as Kentucky, Indiana, Ohio, and Michigan. The species migrates from the south, where they thrive in the warmer climate, but their late summer numbers to the north this year are extreme.
“We’ve not seen anything like this before,” said Christian Krupke, a field crop entomologist at Purdue University.
Krupke said the fall armyworm likes to eat the leaves on many kinds of vegetation but prefer young plants leaving crops like hay and late-planted soybeans especially vulnerable. Once the leaves are gone, the plants are no longer able to generate the energy from the sun they need to survive. Depending on density and size, Fall armyworms can decimate a field practically overnight before marching in a group to the next and closest food source, he said.
Krupke said armyworms begin as larvae and turn into caterpillars before going underground to transform into moths. He said signs of a bumper crop in the Midwest emerged about a month ago when fall armyworm moths in large numbers were detected coming up from Kentucky.
In response, Purdue University issued an advisory to farmers to scout for the predators in their fields.
Armyworms also like many types of grass and other plants such as alfalfa, corn, beets, cabbage, and onions. However, Krupke said late-planted crops like corn and soybeans are too mature this time of year to attract many species, and not every grower of still young plants will be impacted.
However, Krupke said the chances of infestation are “decent,” and producers especially vulnerable to the species right now should pay close attention to their fields.
“Anyone that is growing forage, particularly alfalfa, would be prudent to have a look,” he said.
Krupke said an insecticide applied at dusk or dawn is very effective in killing armyworms while they’re young. Controlling them is more complex, though, as they become larger and more resistant to the chemicals. Nevertheless, the Midwest invasion is already easing up in the more southern areas.
Krupke expects the threat further north to start diminishing in mid-September when the species, after reaching maximum growth, burrows into the soil to become a moth.